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Inoue R, Tsuno T, Togashi Y, Okuyama T, Sato A, Nishiyama K, Kyohara M, Li J, Fukushima S, Kin T, Miyashita D, Shiba Y, Atobe Y, Kiyonari H, Bando K, Shapiro AJ, Funakoshi K, Kulkarni RN, Terauchi Y, Shirakawa J. Uncoupling protein 2 and aldolase B impact insulin release by modulating mitochondrial function and Ca 2+ release from the ER. iScience 2022; 25:104603. [PMID: 35800776 PMCID: PMC9253497 DOI: 10.1016/j.isci.2022.104603] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 03/25/2022] [Accepted: 06/08/2022] [Indexed: 02/02/2023] Open
Abstract
Uncoupling protein 2 (UCP2), a mitochondrial protein, is known to be upregulated in pancreatic islets of patients with type 2 diabetes (T2DM); however, the pathological significance of this increase in UCP2 expression is unclear. In this study, we highlight the molecular link between the increase in UCP2 expression in β-cells and β-cell failure by using genetically engineered mice and human islets. β-cell-specific UCP2-overexpressing transgenic mice (βUCP2Tg) exhibited glucose intolerance and a reduction in insulin secretion. Decreased mitochondrial function and increased aldolase B (AldB) expression through oxidative-stress-mediated pathway were observed in βUCP2Tg islets. AldB, a glycolytic enzyme, was associated with reduced insulin secretion via mitochondrial dysfunction and impaired calcium release from the endoplasmic reticulum (ER). Taken together, our findings provide a new mechanism of β-cell dysfunction by UCP2 and AldB. Targeting the UCP2/AldB axis is a promising approach for the recovery of β-cell function.
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Affiliation(s)
- Ryota Inoue
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Takahiro Tsuno
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yu Togashi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Tomoko Okuyama
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Aoi Sato
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
| | - Kuniyuki Nishiyama
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Mayu Kyohara
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Jinghe Li
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Setsuko Fukushima
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
| | - Tatsuya Kin
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, AB T6G2C8, Canada
| | - Daisuke Miyashita
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yusuke Shiba
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Yoshitoshi Atobe
- Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama 236-0004, Japan
| | - Hiroshi Kiyonari
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - Kana Bando
- Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Biosystems Dynamics Research, Kobe 650-0047, Japan
| | - A.M. James Shapiro
- Clinical Islet Laboratory and Clinical Islet Transplant Program, University of Alberta, Edmonton, AB T6G2C8, Canada
| | - Kengo Funakoshi
- Department of Neuroanatomy, Yokohama City University School of Medicine, Yokohama 236-0004, Japan
| | - Rohit N. Kulkarni
- Islet Cell and Regenerative Biology, Joslin Diabetes Center, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02215, USA
| | - Yasuo Terauchi
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
| | - Jun Shirakawa
- Laboratory of Diabetes and Metabolic Disorders, Institute for Molecular and Cellular Regulation (IMCR), Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan
- Department of Endocrinology and Metabolism, Graduate School of Medicine, Yokohama City University, Yokohama 236-0004, Japan
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Shyr ZA, Wang Z, York NW, Nichols CG, Remedi MS. The role of membrane excitability in pancreatic β-cell glucotoxicity. Sci Rep 2019; 9:6952. [PMID: 31061431 PMCID: PMC6502887 DOI: 10.1038/s41598-019-43452-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 01/11/2019] [Indexed: 01/09/2023] Open
Abstract
Persistent hyperglycemia is causally associated with pancreatic β-cell dysfunction and loss of pancreatic insulin. Glucose normally enhances β-cell excitability through inhibition of KATP channels, opening of voltage-dependent calcium channels, increased [Ca2+]i, which triggers insulin secretion. Glucose-dependent excitability is lost in islets from KATP-knockout (KATP-KO) mice, in which β-cells are permanently hyperexcited, [Ca2+]i, is chronically elevated and insulin is constantly secreted. Mouse models of human neonatal diabetes in which KATP gain-of-function mutations are expressed in β-cells (KATP-GOF) also lose the link between glucose metabolism and excitation-induced insulin secretion, but in this case KATP-GOF β-cells are chronically underexcited, with permanently low [Ca2+]i and lack of glucose-dependent insulin secretion. We used KATP-GOF and KATP-KO islets to examine the role of altered-excitability in glucotoxicity. Wild-type islets showed rapid loss of insulin content when chronically incubated in high-glucose, an effect that was reversed by subsequently switching to low glucose media. In contrast, hyperexcitable KATP-KO islets lost insulin content in both low- and high-glucose, while underexcitable KATP-GOF islets maintained insulin content in both conditions. Loss of insulin content in chronic excitability was replicated by pharmacological inhibition of KATP by glibenclamide, The effects of hyperexcitable and underexcitable islets on glucotoxicity observed in in vivo animal models are directly opposite to the effects observed in vitro: we clearly demonstrate here that in vitro, hyperexcitability is detrimental to islets whereas underexcitability is protective.
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Affiliation(s)
- Zeenat A Shyr
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
| | - Zhiyu Wang
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA.,Endocrine Consultants Northwest, Franciscan Medical Group, 1628 South Mildred St. Suite 104, Tacoma, WA, 98465, USA
| | - Nathaniel W York
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
| | - Maria S Remedi
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA. .,Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA. .,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA.
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Kelly AC, Bidwell CA, Chen X, Macko AR, Anderson MJ, Limesand SW. Chronic Adrenergic Signaling Causes Abnormal RNA Expression of Proliferative Genes in Fetal Sheep Islets. Endocrinology 2018; 159:3565-3578. [PMID: 30124804 PMCID: PMC6150948 DOI: 10.1210/en.2018-00540] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 08/10/2018] [Indexed: 12/22/2022]
Abstract
Intrauterine growth restriction (IUGR) increases the risk of developing diabetes in later life, which indicates developmental programming of islets. IUGR fetuses with placental insufficiency develop hypoxemia, elevating epinephrine and norepinephrine (NE) concentrations throughout late gestation. To isolate the programming effects of chronically elevated catecholamines, NE was continuously infused into normally grown sheep fetuses for 7 days. High plasma NE concentrations suppress insulin, but after the NE infusion was terminated, persistent hypersecretion of insulin occurred. Our objective was to identify differential gene expression with RNA sequencing (RNAseq) in fetal islets after chronic adrenergic stimulation. After determining the NE-regulated genes, we identified the subset of differentially expressed genes that were common to both islets from NE fetuses and fetuses with IUGR to delineate the adrenergic-induced transcriptional responses. A portion of these genes were investigated in mouse insulinoma (Min6) cells chronically treated with epinephrine to better approximate the β-cell response. In islets from NE fetuses, RNAseq identified 321 differentially expressed genes that were overenriched for metabolic and hormone processes, and the subset of 96 differentially expressed genes common to IUGR islets were overenriched for protein digestion, vitamin metabolism, and cell replication pathways. Thirty-eight of the 96 NE-regulated IUGR genes changed similarly between models with functional enrichment for proliferation. In Min6 cells, chronic epinephrine stimulation slowed proliferation and augmented insulin secretion after treatment. These data establish molecular mechanisms underlying persistent adrenergic stimulation in hyperfunctional fetal islets and identify a subset of genes dysregulated by catecholamines in IUGR islets that may represent programming of β-cell proliferation capacity.
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Affiliation(s)
- Amy C Kelly
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | | | - Xiaochuan Chen
- Chongqing Key Laboratory of Forage & Herbivore, College of Animal Science and Technology, Southwest University, Chongqing, China
| | - Antoni R Macko
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Miranda J Anderson
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
| | - Sean W Limesand
- School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, Arizona
- Correspondence: Sean W. Limesand, PhD, School of Animal and Comparative Biomedical Sciences, University of Arizona, 1650 East Limberlost Drive, Tucson, Arizona 85719. E-mail:
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Bensellam M, Jonas JC, Laybutt DR. Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions. J Endocrinol 2018; 236:R109-R143. [PMID: 29203573 DOI: 10.1530/joe-17-0516] [Citation(s) in RCA: 158] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 12/04/2017] [Indexed: 12/13/2022]
Abstract
Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.
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Affiliation(s)
- Mohammed Bensellam
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Jean-Christophe Jonas
- Université Catholique de LouvainInstitut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - D Ross Laybutt
- Garvan Institute of Medical ResearchSydney, New South Wales, Australia
- St Vincent's Clinical SchoolUNSW Sydney, Sydney, New South Wales, Australia
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Hals IK, Singh R, Ma Z, Scholz H, Björklund A, Grill V. Culture at low glucose up-regulates mitochondrial function in pancreatic β cells with accompanying effects on viability. Islets 2016; 8:165-176. [PMID: 27763807 PMCID: PMC5161144 DOI: 10.1080/19382014.2016.1246637] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
We tested whether exposure of β cells at reduced glucose leads to mitochondrial adaptions and whether such adaptions modulate effects of hypoxia. Rat islets, human islets and INS-1 832/13 cells were pre-cultured short term at half standard glucose concentrations (5.5 mM for rat islets and cells, 2.75 mM for human islets) without overtly negative effects on subsequently measured function (insulin secretion and cellular insulin contents) or on viability. Culture at half standard glucose upregulated complex I and tended to upregulate complex II in islets and INS-1 cells alike. An increased release of lactate dehydrogenase that followed exposure to hypoxia was attenuated in rat islets which had been pre-cultured at half standard glucose. In INS-1 cells exposure to half standard glucose attenuated hypoxia-induced effects on several viability parameters (MTT, cell number and incremental apoptotic DNA). Thus culture at reduced glucose of pancreatic islets and clonal β cells leads to mitochondrial adaptions which possibly lessen the negative impact of hypoxia on β cell viability. These findings appear relevant in the search for optimization of pre-transplant conditions in a clinical setting.
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Affiliation(s)
- Ingrid K. Hals
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- Department of Endocrinology, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway
- CONTACT Ingrid K. Hals Department of Cancer Research and Molecular Medicine, NTNU, Gastrosenter, St Olavs Hospital, Prinsesse Kristinas gate 1, 7006 Trondheim, Norway
| | - Rinku Singh
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Zuheng Ma
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Hanne Scholz
- Department of Transplantation Medicine and Institute for Surgical Research, Oslo University Hospital, Oslo, Norway
| | - Anneli Björklund
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Valdemar Grill
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- Department of Endocrinology, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway
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Gregg T, Poudel C, Schmidt BA, Dhillon RS, Sdao SM, Truchan NA, Baar EL, Fernandez LA, Denu JM, Eliceiri KW, Rogers JD, Kimple ME, Lamming DW, Merrins MJ. Pancreatic β-Cells From Mice Offset Age-Associated Mitochondrial Deficiency With Reduced KATP Channel Activity. Diabetes 2016; 65:2700-10. [PMID: 27284112 PMCID: PMC5001174 DOI: 10.2337/db16-0432] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 05/31/2016] [Indexed: 12/20/2022]
Abstract
Aging is accompanied by impaired glucose homeostasis and an increased risk of type 2 diabetes, culminating in the failure of insulin secretion from pancreatic β-cells. To investigate the effects of age on β-cell metabolism, we established a novel assay to directly image islet metabolism with NAD(P)H fluorescence lifetime imaging (FLIM). We determined that impaired mitochondrial activity underlies an age-dependent loss of insulin secretion in human islets. NAD(P)H FLIM revealed a comparable decline in mitochondrial function in the pancreatic islets of aged mice (≥24 months), the result of 52% and 57% defects in flux through complex I and II, respectively, of the electron transport chain. However, insulin secretion and glucose tolerance are preserved in aged mouse islets by the heightened metabolic sensitivity of the β-cell triggering pathway, an adaptation clearly encoded in the metabolic and Ca(2+) oscillations that trigger insulin release (Ca(2+) plateau fraction: young 0.211 ± 0.006, aged 0.380 ± 0.007, P < 0.0001). This enhanced sensitivity is driven by a reduction in KATP channel conductance (diazoxide: young 5.1 ± 0.2 nS; aged 3.5 ± 0.5 nS, P < 0.01), resulting in an ∼2.8 mmol/L left shift in the β-cell glucose threshold. The results demonstrate how mice but not humans are able to successfully compensate for age-associated metabolic dysfunction by adjusting β-cell glucose sensitivity and highlight an essential mechanism for ensuring the maintenance of insulin secretion.
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Affiliation(s)
- Trillian Gregg
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI Biophysics Graduate Training Program, University of Wisconsin-Madison, Madison, WI Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI
| | - Chetan Poudel
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI
| | - Brian A Schmidt
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI
| | - Rashpal S Dhillon
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI
| | - Sophia M Sdao
- Integrated Program in Biochemistry, University of Wisconsin-Madison, Madison, WI
| | - Nathan A Truchan
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI
| | - Emma L Baar
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI
| | - Luis A Fernandez
- Department of Surgery, Division of Transplantation, University of Wisconsin-Madison, Madison, WI
| | - John M Denu
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI
| | - Kevin W Eliceiri
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI
| | - Jeremy D Rogers
- Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI
| | - Michelle E Kimple
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI William S. Middleton Memorial Veterans Hospital, Madison, WI
| | - Dudley W Lamming
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI William S. Middleton Memorial Veterans Hospital, Madison, WI
| | - Matthew J Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison, Madison, WI Laboratory for Optical and Computational Instrumentation, University of Wisconsin-Madison, Madison, WI Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI William S. Middleton Memorial Veterans Hospital, Madison, WI
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Neuroprotective and Therapeutic Strategies against Parkinson's Disease: Recent Perspectives. Int J Mol Sci 2016; 17:ijms17060904. [PMID: 27338353 PMCID: PMC4926438 DOI: 10.3390/ijms17060904] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 05/27/2016] [Accepted: 05/30/2016] [Indexed: 12/18/2022] Open
Abstract
Parkinsonism is a progressive motor disease that affects 1.5 million Americans and is the second most common neurodegenerative disease after Alzheimer’s. Typical neuropathological features of Parkinson’s disease (PD) include degeneration of dopaminergic neurons located in the pars compacta of the substantia nigra that project to the striatum (nigro-striatal pathway) and depositions of cytoplasmic fibrillary inclusions (Lewy bodies) which contain ubiquitin and α-synuclein. The cardinal motor signs of PD are tremors, rigidity, slow movement (bradykinesia), poor balance, and difficulty in walking (Parkinsonian gait). In addition to motor symptoms, non-motor symptoms that include autonomic and psychiatric as well as cognitive impairments are pressing issues that need to be addressed. Several different mechanisms play an important role in generation of Lewy bodies; endoplasmic reticulum (ER) stress induced unfolded proteins, neuroinflammation and eventual loss of dopaminergic neurons in the substantia nigra of mid brain in PD. Moreover, these diverse processes that result in PD make modeling of the disease and evaluation of therapeutics against this devastating disease difficult. Here, we will discuss diverse mechanisms that are involved in PD, neuroprotective and therapeutic strategies currently in clinical trial or in preclinical stages, and impart views about strategies that are promising to mitigate PD pathology.
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Glynn E, Thompson B, Vadrevu S, Lu S, Kennedy RT, Ha J, Sherman A, Satin LS. Chronic Glucose Exposure Systematically Shifts the Oscillatory Threshold of Mouse Islets: Experimental Evidence for an Early Intrinsic Mechanism of Compensation for Hyperglycemia. Endocrinology 2016; 157:611-23. [PMID: 26697721 PMCID: PMC4733117 DOI: 10.1210/en.2015-1563] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mouse islets exhibit glucose-dependent oscillations in electrical activity, intracellular Ca(2+) and insulin secretion. We developed a mathematical model in which a left shift in glucose threshold helps compensate for insulin resistance. To test this experimentally, we exposed isolated mouse islets to varying glucose concentrations overnight and monitored their glucose sensitivity the next day by measuring intracellular Ca(2+), electrical activity, and insulin secretion. Glucose sensitivity of all oscillation modes was increased when overnight glucose was greater than 2.8mM. To determine whether threshold shifts were a direct effect of glucose or involved secreted insulin, the KATP opener diazoxide (Dz) was coapplied with glucose to inhibit insulin secretion. The addition of Dz or the insulin receptor antagonist s961 increased islet glucose sensitivity, whereas the KATP blocker tolbutamide tended to reduce it. This suggests insulin and glucose have opposing actions on the islet glucose threshold. To test the hypothesis that the threshold shifts were due to changes in plasma membrane KATP channels, we measured cell KATP conductance, which was confirmed to be reduced by high glucose pretreatment and further reduced by Dz. Finally, treatment of INS-1 cells with glucose and Dz overnight reduced high affinity sulfonylurea receptor (SUR1) trafficking to the plasma membrane vs glucose alone, consistent with insulin increasing KATP conductance by altering channel number. The results support a role for metabolically regulated KATP channels in the maintenance of glucose homeostasis.
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Affiliation(s)
- Eric Glynn
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Benjamin Thompson
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Suryakiran Vadrevu
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Shusheng Lu
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Robert T Kennedy
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Joon Ha
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Arthur Sherman
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Leslie S Satin
- Department of Pharmacology and Brehm Diabetes Research Center (E.G., B.T., S.V., L.S.S.) and Department of Chemistry (S.L., R.T.K.), University of Michigan, Ann Arbor, Michigan 48105; and Laboratory of Biological Modeling (J.H., A.S.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892
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Hals IK, Bruerberg SG, Ma Z, Scholz H, Björklund A, Grill V. Mitochondrial Respiration in Insulin-Producing β-Cells: General Characteristics and Adaptive Effects of Hypoxia. PLoS One 2015; 10:e0138558. [PMID: 26401848 PMCID: PMC4581632 DOI: 10.1371/journal.pone.0138558] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Accepted: 09/01/2015] [Indexed: 01/04/2023] Open
Abstract
Objective To provide novel insights on mitochondrial respiration in β-cells and the adaptive effects of hypoxia. Methods and Design Insulin-producing INS-1 832/13 cells were exposed to 18 hours of hypoxia followed by 20–22 hours re-oxygenation. Mitochondrial respiration was measured by high-resolution respirometry in both intact and permeabilized cells, in the latter after establishing three functional substrate-uncoupler-inhibitor titration (SUIT) protocols. Concomitant measurements included proteins of mitochondrial complexes (Western blotting), ATP and insulin secretion. Results Intact cells exhibited a high degree of intrinsic uncoupling, comprising about 50% of oxygen consumption in the basal respiratory state. Hypoxia followed by re-oxygenation increased maximal overall respiration. Exploratory experiments in peremabilized cells could not show induction of respiration by malate or pyruvate as reducing substrates, thus glutamate and succinate were used as mitochondrial substrates in SUIT protocols. Permeabilized cells displayed a high capacity for oxidative phosphorylation for both complex I- and II-linked substrates in relation to maximum capacity of electron transfer. Previous hypoxia decreased phosphorylation control of complex I-linked respiration, but not in complex II-linked respiration. Coupling control ratios showed increased coupling efficiency for both complex I- and II-linked substrates in hypoxia-exposed cells. Respiratory rates overall were increased. Also previous hypoxia increased proteins of mitochondrial complexes I and II (Western blotting) in INS-1 cells as well as in rat and human islets. Mitochondrial effects were accompanied by unchanged levels of ATP, increased basal and preserved glucose-induced insulin secretion. Conclusions Exposure of INS-1 832/13 cells to hypoxia, followed by a re-oxygenation period increases substrate-stimulated respiratory capacity and coupling efficiency. Such effects are accompanied by up-regulation of mitochondrial complexes also in pancreatic islets, highlighting adaptive capacities of possible importance in an islet transplantation setting. Results also indicate idiosyncrasies of β-cells that do not respire in response to a standard inclusion of malate in SUIT protocols.
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Affiliation(s)
- Ingrid K. Hals
- Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- * E-mail:
| | - Simon Gustafson Bruerberg
- Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Zuheng Ma
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Hanne Scholz
- Department of Transplantation Medicine and Institute for Surgical Research, Oslo University Hospital, Oslo, Norway
| | - Anneli Björklund
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Valdemar Grill
- Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
- Department of Endocrinology, St Olav University Hospital, Trondheim, Norway
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10
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Prolonged hyperglycemia & hyperinsulinemia increases BDNF mRNA expression in the posterior ventromedial hypothalamus and the dorsomedial hypothalamus of fed female rats. Neuroscience 2015; 303:422-32. [DOI: 10.1016/j.neuroscience.2015.07.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 07/02/2015] [Accepted: 07/05/2015] [Indexed: 12/30/2022]
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11
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Ma Z, Moruzzi N, Catrina SB, Grill V, Björklund A. Hyperoxia inhibits glucose-induced insulin secretion and mitochondrial metabolism in rat pancreatic islets. Biochem Biophys Res Commun 2013; 443:223-8. [PMID: 24299957 DOI: 10.1016/j.bbrc.2013.11.088] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 11/22/2013] [Indexed: 12/30/2022]
Abstract
Isolated pancreatic islets containing the insulin-producing beta cells are devoid of circulation. They may therefore experience hypoxia with possible negative effects on beta cell function and survival. We investigated (1) whether hyperoxia in vitro would be beneficial by counteracting putative effects of lost circulation and, further, (2) whether previous hyperoxia would attenuate the impact of subsequently induced severe hypoxia. Islets from Sprague-Dawley rats were exposed to 95% O2 for 18 h. This hyperoxic exposure diminished glucose-induced insulin secretion by 47% and inhibited oxygen consumption by 39-41%. Mitochondrial complexes I-III were decreased by 29-37%. Negative effects on insulin secretion and complexes III and IV waned after a 22 h period of normoxia following hyperoxia whereas complexes I and II were still diminished, ROS production was increased and rates of apoptosis tended to be increased (P=0.07). The effects of previous hyperoxia on susceptibility to damage by subsequent hypoxia were tested after 5.5h of 0.8% O2. Previous hyperoxia did not affect hypoxia-induced enhancement of HIF-1 alpha but modestly and significantly attenuated hypoxia-induced decreases in insulin contents. We conclude that hyperoxia exerts largely negative effects on beta cells, effects which are functional and possibly also toxic. A paradoxical positive finding (attenuation of hypoxia-induced effects) could be secondary to a protective effect of the hyperoxia-induced reduction of oxidative metabolism.
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Affiliation(s)
- Zuheng Ma
- Dept. of Molecular Medicine and Surgery, Karolinska Institutet, 171 76 Stockholm, Sweden
| | - Noah Moruzzi
- Dept. of Molecular Medicine and Surgery, Karolinska Institutet, 171 76 Stockholm, Sweden
| | - Sergiu-Bogdan Catrina
- Dept. of Molecular Medicine and Surgery, Karolinska Institutet, 171 76 Stockholm, Sweden
| | - Valdemar Grill
- Dept. of Molecular Medicine and Surgery, Karolinska Institutet, 171 76 Stockholm, Sweden; Institute of Cancer Research and Molecular Medicine, The Medical Faculty, Norwegian University of Science and Technology, 7006 Trondheim, Norway; Dept. of Endocrinology, St. Olav University Hospital, 7006 Trondheim, Norway
| | - Anneli Björklund
- Dept. of Molecular Medicine and Surgery, Karolinska Institutet, 171 76 Stockholm, Sweden.
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12
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Ma Z, Moruzzi N, Catrina SB, Hals I, Oberholzer J, Grill V, Björklund A. Preconditioning with associated blocking of Ca2+ inflow alleviates hypoxia-induced damage to pancreatic β-cells. PLoS One 2013; 8:e67498. [PMID: 23935835 PMCID: PMC3723782 DOI: 10.1371/journal.pone.0067498] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 05/20/2013] [Indexed: 01/06/2023] Open
Abstract
Objective Beta cells of pancreatic islets are susceptible to functional deficits and damage by hypoxia. Here we aimed to characterize such effects and to test for and pharmacological means to alleviate a negative impact of hypoxia. Methods and Design Rat and human pancreatic islets were subjected to 5.5 h of hypoxia after which functional and viability parameters were measured subsequent to the hypoxic period and/or following a 22 h re-oxygenation period. Preconditioning with diazoxide or other agents was usually done during a 22 h period prior to hypoxia. Results Insulin contents decreased by 23% after 5.5 h of hypoxia and by 61% after a re-oxygenation period. Preconditioning with diazoxide time-dependently alleviated these hypoxia effects in rat and human islets. Hypoxia reduced proinsulin biosynthesis (3H-leucine incorporation into proinsulin) by 35%. Preconditioning counteracted this decrease by 91%. Preconditioning reduced hypoxia-induced necrosis by 40%, attenuated lowering of proteins of mitochondrial complexes I–IV and enhanced stimulation of HIF-1-alpha and phosphorylated AMPK proteins. Preconditioning by diazoxide was abolished by co-exposure to tolbutamide or elevated potassium (i.e. conditions which increase Ca2+ inflow). Preconditioning with nifedipine, a calcium channel blocker, partly reproduced effects of diazoxide. Both diazoxide and nifedipine moderately reduced basal glucose oxidation whereas glucose-induced oxygen consumption (tested with diazoxide) was unaffected. Preconditioning with diaxoxide enhanced insulin contents in transplants of rat islets to non-diabetic rats and lowered hyperglycemia vs. non-preconditioned islets in streptozotocin-diabetic rats. Preconditioning of human islet transplants lowered hyperglycemia in streptozotocin-diabetic nude mice. Conclusions 1) Prior blocking of Ca2+ inflow associates with lesser hypoxia-induced damage, 2) preconditioning affects basal mitochondrial metabolism and accelerates activation of hypoxia-reactive and potentially protective factors, 3) results indicate that preconditioning by K+-ATP-channel openers has therapeutic potential for islet transplantations.
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Affiliation(s)
- Zuheng Ma
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Noah Moruzzi
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Sergiu-Bogdan Catrina
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Ingrid Hals
- Institute of Cancer Research and Molecular Medicine, The Medical Faculty, Norwegian University of Science and Technology, Trondheim, Norway
| | - José Oberholzer
- Department of Transplant/Surgery, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Valdemar Grill
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
- Institute of Cancer Research and Molecular Medicine, The Medical Faculty, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Endocrinology, St. Olav University Hospital, 7006 Trondheim, Norway
| | - Anneli Björklund
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
- * E-mail:
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13
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Hectors TLM, Vanparys C, Pereira-Fernandes A, Martens GA, Blust R. Evaluation of the INS-1 832/13 cell line as a beta-cell based screening system to assess pollutant effects on beta-cell function. PLoS One 2013; 8:e60030. [PMID: 23555872 PMCID: PMC3605429 DOI: 10.1371/journal.pone.0060030] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 02/22/2013] [Indexed: 01/15/2023] Open
Abstract
Environmental pollutants have recently emerged as potential risk factors for metabolic diseases, urging systematic investigation of pollutant effects on metabolic disease processes. To enable risk assessment of these so-called metabolic disruptors the use of stable, robust and well-defined cell based screening systems has recently been encouraged. Since beta-cell (dys)functionality is central in diabetes pathophysiology, the need to develop beta-cell based pollutant screening systems is evident. In this context, the present research evaluated the strengths and weaknesses of the INS-1 832/13 pancreatic beta-cell line as diabetogenic pollutant screening system with a focus on beta-cell function. After optimization of exposure conditions, positive (exendin-4, glibenclamide) and negative (diazoxide) control compounds for acute insulin secretion responses were tested and those with the most profound effects were selected to allow potency estimations and ranking of pollutants. This was followed by a first explorative screening of acute bisphenol A and bis(2-ethylhexyl)phthalate effects. The same approach was applied for chronic exposures, focusing primarily on evaluation of acknowledged chronic stimulators (diazoxide, T0901317, exendin-4) or inhibitors (glibenclamide) of insulin secretion responses to select the most responsive ones for use as control compounds in a chronic pollutant testing framework. Our results showed that INS-1 832/13 cells responded conform previous observations regarding acute effects of control compounds on insulin secretion, while bisphenol A and bis(2-ethylhexyl)phthalate had limited acute effects. Furthermore, chronic exposure to known beta-cell reactive compounds resulted in deviating insulin secretion and insulin content profiles compared to previous reports. In conclusion, this INS-1 subclone appears to lack certain characteristics needed to respond appropriately to acute pollutant exposure or long term exposure to known beta-cell reactive compounds and thus seems to be, in our setting, inadequate as a diabetogenic pollutant screening system.
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Affiliation(s)
- Tine L M Hectors
- Systemic Physiological and Ecotoxicological Research, Department of Biology, University of Antwerp, Antwerp, Belgium.
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14
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Bensellam M, Laybutt DR, Jonas JC. The molecular mechanisms of pancreatic β-cell glucotoxicity: recent findings and future research directions. Mol Cell Endocrinol 2012; 364:1-27. [PMID: 22885162 DOI: 10.1016/j.mce.2012.08.003] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/11/2012] [Accepted: 08/01/2012] [Indexed: 02/06/2023]
Abstract
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the β-cell differentiated phenotype. In contrast, prolonged or repeated exposure to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the β-cell phenotype, a concept termed as glucotoxicity. Evidence indicates that the latter may greatly contribute to the pathogenesis of type 2 diabetes. Through the activation of several mechanisms and signaling pathways, high glucose levels exert deleterious effects on β-cell function and survival and thereby, lead to the worsening of the disease over time. While the role of high glucose-induced β-cell overstimulation, oxidative stress, excessive Unfolded Protein Response (UPR) activation, and loss of differentiation in the alteration of the β-cell phenotype is well ascertained, at least in vitro and in animal models of type 2 diabetes, the role of other mechanisms such as inflammation, O-GlcNacylation, PKC activation, and amyloidogenesis requires further confirmation. On the other hand, protein glycation is an emerging mechanism that may play an important role in the glucotoxic deterioration of the β-cell phenotype. Finally, our recent evidence suggests that hypoxia may also be a new mechanism of β-cell glucotoxicity. Deciphering these molecular mechanisms of β-cell glucotoxicity is a mandatory first step toward the development of therapeutic strategies to protect β-cells and improve the functional β-cell mass in type 2 diabetes.
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Affiliation(s)
- Mohammed Bensellam
- Université catholique de Louvain, Institut de recherche expérimentale et clinique, Pôle d'endocrinologie, diabète et nutrition, Brussels, Belgium
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15
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Hals IK, Ogata H, Pettersen E, Ma Z, Björklund A, Skorpen F, Egeberg KW, Grill V. Marked over expression of uncoupling protein-2 in beta cells exerts minor effects on mitochondrial metabolism. Biochem Biophys Res Commun 2012; 423:259-64. [DOI: 10.1016/j.bbrc.2012.05.101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 05/17/2012] [Indexed: 11/17/2022]
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16
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Lynch CJ, Zhou Q, Shyng SL, Heal DJ, Cheetham SC, Dickinson K, Gregory P, Firnges M, Nordheim U, Goshorn S, Reiche D, Turski L, Antel J. Some cannabinoid receptor ligands and their distomers are direct-acting openers of SUR1 K(ATP) channels. Am J Physiol Endocrinol Metab 2012; 302:E540-51. [PMID: 22167524 PMCID: PMC3311290 DOI: 10.1152/ajpendo.00250.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Here, we examined the chronic effects of two cannabinoid receptor-1 (CB1) inverse agonists, rimonabant and ibipinabant, in hyperinsulinemic Zucker rats to determine their chronic effects on insulinemia. Rimonabant and ibipinabant (10 mg·kg⁻¹·day⁻¹) elicited body weight-independent improvements in insulinemia and glycemia during 10 wk of chronic treatment. To elucidate the mechanism of insulin lowering, acute in vivo and in vitro studies were then performed. Surprisingly, chronic treatment was not required for insulin lowering. In acute in vivo and in vitro studies, the CB1 inverse agonists exhibited acute K channel opener (KCO; e.g., diazoxide and NN414)-like effects on glucose tolerance and glucose-stimulated insulin secretion (GSIS) with approximately fivefold better potency than diazoxide. Followup studies implied that these effects were inconsistent with a CB1-mediated mechanism. Thus effects of several CB1 agonists, inverse agonists, and distomers during GTTs or GSIS studies using perifused rat islets were unpredictable from their known CB1 activities. In vivo rimonabant and ibipinabant caused glucose intolerance in CB1 but not SUR1-KO mice. Electrophysiological studies indicated that, compared with diazoxide, 3 μM rimonabant and ibipinabant are partial agonists for K channel opening. Partial agonism was consistent with data from radioligand binding assays designed to detect SUR1 K(ATP) KCOs where rimonabant and ibipinabant allosterically regulated ³H-glibenclamide-specific binding in the presence of MgATP, as did diazoxide and NN414. Our findings indicate that some CB1 ligands may directly bind and allosterically regulate Kir6.2/SUR1 K(ATP) channels like other KCOs. This mechanism appears to be compatible with and may contribute to their acute and chronic effects on GSIS and insulinemia.
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MESH Headings
- ATP-Binding Cassette Transporters/agonists
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Allosteric Regulation
- Animals
- Anti-Obesity Agents/adverse effects
- Anti-Obesity Agents/chemistry
- Anti-Obesity Agents/pharmacology
- Anti-Obesity Agents/therapeutic use
- Cell Line, Transformed
- Chlorocebus aethiops
- Cricetinae
- Glucose Intolerance/chemically induced
- Glucose Intolerance/metabolism
- Humans
- Hypoglycemic Agents/adverse effects
- Hypoglycemic Agents/chemistry
- Hypoglycemic Agents/pharmacology
- Hypoglycemic Agents/therapeutic use
- Islets of Langerhans/drug effects
- Islets of Langerhans/metabolism
- Ligands
- Male
- Membrane Transport Modulators/adverse effects
- Membrane Transport Modulators/chemistry
- Membrane Transport Modulators/pharmacology
- Membrane Transport Modulators/therapeutic use
- Mice
- Mice, Knockout
- Mice, Obese
- Potassium Channels, Inwardly Rectifying/agonists
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Rats
- Rats, Zucker
- Receptor, Cannabinoid, CB1/agonists
- Receptor, Cannabinoid, CB1/antagonists & inhibitors
- Receptor, Cannabinoid, CB1/genetics
- Receptor, Cannabinoid, CB1/metabolism
- Receptors, Drug/agonists
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Recombinant Proteins/agonists
- Recombinant Proteins/antagonists & inhibitors
- Recombinant Proteins/metabolism
- Stereoisomerism
- Sulfonylurea Receptors
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Affiliation(s)
- Christopher J Lynch
- Dept. of Cellular & Molecular Physiology, Pennsylvania State College of Medicine, Hershey, PA 17033, USA.
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17
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Bensellam M, Duvillié B, Rybachuk G, Laybutt DR, Magnan C, Guiot Y, Pouysségur J, Jonas JC. Glucose-induced O₂ consumption activates hypoxia inducible factors 1 and 2 in rat insulin-secreting pancreatic beta-cells. PLoS One 2012; 7:e29807. [PMID: 22235342 PMCID: PMC3250482 DOI: 10.1371/journal.pone.0029807] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Accepted: 12/06/2011] [Indexed: 12/21/2022] Open
Abstract
Background Glucose increases the expression of glycolytic enzymes and other hypoxia-response genes in pancreatic beta-cells. Here, we tested whether this effect results from the activation of Hypoxia-Inducible-factors (HIF) 1 and 2 in a hypoxia-dependent manner. Methodology/Principal Findings Isolated rat islets and insulin-secreting INS-1E cells were stimulated with nutrients at various pO2 values or treated with the HIF activator CoCl2. HIF-target gene mRNA levels and HIF subunit protein levels were measured by real-time RT-PCR, Western Blot and immunohistochemistry. The formation of pimonidazole-protein adducts was used as an indicator of hypoxia. In INS-1E and islet beta-cells, glucose concentration-dependently stimulated formation of pimonidazole-protein adducts, HIF1 and HIF2 nuclear expression and HIF-target gene mRNA levels to a lesser extent than CoCl2 or a four-fold reduction in pO2. Islets also showed signs of HIF activation in diabetic Leprdb/db but not non-diabetic Leprdb/+ mice. In vitro, these glucose effects were reproduced by nutrient secretagogues that bypass glycolysis, and were inhibited by a three-fold increase in pO2 or by inhibitors of Ca2+ influx and insulin secretion. In INS-1E cells, small interfering RNA-mediated knockdown of Hif1α and Hif2α, alone or in combination, indicated that the stimulation of glycolytic enzyme mRNA levels depended on both HIF isoforms while the vasodilating peptide adrenomedullin was a HIF2-specific target gene. Conclusions/Significance Glucose-induced O2 consumption creates an intracellular hypoxia that activates HIF1 and HIF2 in rat beta-cells, and this glucose effect contributes, together with the activation of other transcription factors, to the glucose stimulation of expression of some glycolytic enzymes and other hypoxia response genes.
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Affiliation(s)
- Mohammed Bensellam
- Pôle d′Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Bertrand Duvillié
- INSERM U845, Faculté de Médecine, Research Center Growth and Signalling, Université Paris Descartes, Hôpital Necker, Paris, France
| | - Galyna Rybachuk
- Pôle d′Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - D. Ross Laybutt
- Diabetes and Obesity Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, Australia
| | - Christophe Magnan
- Unité de Biologie Fonctionnelle et Adaptative, CNRS-Université Paris Diderot-Paris 7, Paris, France
| | - Yves Guiot
- Pôle de Morphologie, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
| | - Jacques Pouysségur
- Institute of Developmental Biology and Cancer Research, University of Nice, CNRS UMR 6543, Centre A. Lacassagne, Nice, France
| | - Jean-Christophe Jonas
- Pôle d′Endocrinologie, Diabète et Nutrition, Institut de Recherche Expérimentale et Clinique, Université Catholique de Louvain, Brussels, Belgium
- * E-mail:
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18
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Bellomo EA, Meur G, Rutter GA. Glucose regulates free cytosolic Zn²⁺ concentration, Slc39 (ZiP), and metallothionein gene expression in primary pancreatic islet β-cells. J Biol Chem 2011; 286:25778-89. [PMID: 21613223 PMCID: PMC3138249 DOI: 10.1074/jbc.m111.246082] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 05/13/2011] [Indexed: 12/15/2022] Open
Abstract
Zn²⁺ is an important cofactor for insulin biosynthesis and storage in pancreatic β-cells. Correspondingly, polymorphisms in the SLC30A8 gene, encoding the secretory granule Zn²⁺ transporter ZnT8, are associated with type 2 diabetes risk. Using a genetically engineered (FRET)-based sensor (eCALWY-4), we show here that elevated glucose time-dependently increases free cytosolic Zn²⁺ ([Zn²⁺](cyt)) in mouse pancreatic β-cells. These changes become highly significant (853 ± 96 pm versus 452 ± 42 pm, p < 0.001) after 24 h and are associated with increased expression of the Zn²⁺ importer family members Slc39a6, Slc39a7, and Slc39a8, and decreased expression of metallothionein 1 and 2. Arguing that altered expression of the above genes is not due to altered [Zn²⁺](cyt), elevation of extracellular (and intracellular) [Zn²⁺] failed to mimic the effects of high glucose. By contrast, increases in intracellular cAMP prompted by 3-isobutyl-1-methylxanthine and forskolin partially mimicked the effects of glucose on metallothionein, although not ZiP, gene expression. Modulation of intracellular Ca²⁺ and insulin secretion with pharmacological agents (tolbutamide and diazoxide) suggested a possible role for changes in these parameters in the regulation of Slc39a6 and Slc39a7 but not Slc39a8, nor metallothionein expression. In summary, 1) glucose induces increases in [Zn²⁺](cyt), which are then likely to facilitate the processing and/or the storage of insulin and its cocrystallization with Zn²⁺, and 2) these increases are associated with elevated expression of zinc importers. Conversely, a chronic increase in [Zn²⁺](cyt) following sustained hyperglycemia may contribute to β-cell dysfunction and death in some forms of diabetes.
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Affiliation(s)
- Elisa A. Bellomo
- From the Section of Cell Biology, Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, London SW7 2AZ, United Kingdom
| | - Gargi Meur
- From the Section of Cell Biology, Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, London SW7 2AZ, United Kingdom
| | - Guy A. Rutter
- From the Section of Cell Biology, Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Faculty of Medicine, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, London SW7 2AZ, United Kingdom
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19
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Grill V, Radtke M, Qvigstad E, Kollind M, Björklund A. Beneficial effects of K-ATP channel openers in diabetes: an update on mechanisms and clinical experiences. Diabetes Obes Metab 2009; 11 Suppl 4:143-8. [PMID: 19817796 DOI: 10.1111/j.1463-1326.2009.01119.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Stresses associated with the diabetic state participate in the demise of beta-cells and therapies that eliminate or reduce such stresses are much needed. K-ATP channel openers, of which diazoxide is the most studied, are potentially useful because experimental studies show that they can counteract chronic over-stimulation of beta-cells and protect against toxic conditions, including relative hypoxia. Several mechanisms may underlie the beneficial effects of diazoxide; these may include both indirect (counteracting over-stimulation) and direct mitochondrial effects. Side effects of diazoxide have limited its use in human trials. We have tested lower doses than previously of diazoxide and thereby largely eliminated side effects. In this setting, we demonstrate positive effects on beta-cell function in type 2 diabetic patients who were simultaneously treated with bedtime insulin. However, such effects were absent in insulin-naïve patients. In newly diagnosed type 1 diabetic patients, a 6-month intervention with diazoxide failed to result in better preservation of beta-cell function. K-ATP channel openers have a potential to improve beta-cell function in subgroups of type 2 diabetes patients. Analogues of diazoxide with more potency in relation to side effects would heighten the possibilities for K-ATP channel openers to be of therapeutic use in type 1 diabetes.
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Affiliation(s)
- V Grill
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
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20
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Bensellam M, Van Lommel L, Overbergh L, Schuit FC, Jonas JC. Cluster analysis of rat pancreatic islet gene mRNA levels after culture in low-, intermediate- and high-glucose concentrations. Diabetologia 2009; 52:463-76. [PMID: 19165461 DOI: 10.1007/s00125-008-1245-z] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS Survival and function of insulin-secreting pancreatic beta cells are markedly altered by changes in nutrient availability. In vitro, culture in 10 rather than 2 mmol/l glucose improves rodent beta cell survival and function, whereas glucose concentrations above 10 mmol/l are deleterious. METHODS To identify the mechanisms of such beta cell plasticity, we tested the effects of 18 h culture at 2, 5, 10 and 30 mmol/l glucose on the transcriptome of rat islets pre-cultured for 1 week at 10 mmol/l glucose using Affymetrix Rat 230 2.0 arrays. RESULTS Culture in either 2-5 or 30 mmol/l instead of 10 mmol/l glucose markedly impaired beta cell function, while little affecting cell survival. Of about 16,000 probe-sets reliably detected in islets, some 5,000 were significantly up- or downregulated at least 1.4-fold by glucose. Analysis of these probe-sets with GeneCluster software identified ten mRNA profiles with unidirectional up- or downregulation between 2 and 10, 2 and 30, 5 and 10, 5 and 30 or 10 and 30 mmol/l glucose. It also identified eight complex V-shaped or inverse V-shaped profiles with a nadir or peak level of expression in 5 or 10 mmol/l glucose. Analysis of genes belonging to these various clusters using Onto-express and GenMAPP software revealed several signalling and metabolic pathways that may contribute to induction of beta cell dysfunction and apoptosis after culture in low- or high- vs intermediate-glucose concentration. CONCLUSIONS/INTERPRETATION We have identified 18 distinct mRNA profiles of glucose-induced changes in islet gene mRNA levels that should help understand the mechanisms by which glucose affects beta cell survival and function under states of chronic hypo- or hyperglycaemia.
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Affiliation(s)
- M Bensellam
- Unit of Endocrinology and Metabolism, Faculty of Medicine, Université catholique de Louvain, Avenue Hippocrate 55 (UCL5530), 1200, Brussels, Belgium
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Bibliography. Current world literature. Growth and development. Curr Opin Endocrinol Diabetes Obes 2008; 15:79-101. [PMID: 18185067 DOI: 10.1097/med.0b013e3282f4f084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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